JPH03141376A - Developing device - Google Patents

Abstract

PURPOSE:To allow a stagnating developer to be surely blown off without leaking and without generating the dead angle of air blowing in a central part by changing the air blowing rate from both sides so as to attain an unbalance state on both sides. CONSTITUTION:A shutter 21 of a semi-circular shape is freely rotatably provided in the positions facing both air supplying ports 17, 18 in a fan box 14. This shutter 21 is rotated in synchronization with a fan 13 by a shutter revolving shaft 13b rotating integrally and coaxially with the revolving shaft 13a of the fan 13 and the opening rates of the two air supplying ports 17, 18 are continuously and automatically adjusted in the unbalancing directions by the rotation of this shutter 21. The air blowing rates from both blowing out ports 11, 12 are always unbalanced and the generation of the dead angle of the air in the central part is prevented. The stagnating developer is thus surely removed without leaking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device provided in an image forming apparatus such as a copying machine.

[Conventional technology]

In a developing device that uses a one-component developer (hereinafter referred to as toner), a thin layer forming member is pressed against the surface of the developer carrier with a constant pressure. At the same time, the thickness of the toner layer adhering to the surface is regulated, and at the same time, an electric charge is given to the toner by frictional charging between the two, and as a result, the toner adheres to a photoreceptor having a predetermined surface potential and a developed image is formed. . Generally, a developing roller is used as the developer carrier, and a blade is used as the III forming member, so these names will be used in the following description.

In such a developing device, a so-called toner pool occurs in which toner gradually accumulates and accumulates between the blade and the developing roller, and this toner pool pushes up the blade, reducing the contact pressure against the developing roller. . Since such a decrease in contact pressure directly leads to image deterioration, prevention of toner accumulation has become a major issue.

[Problem to be solved by the invention]

Therefore, in the past, as shown in (I) Japanese Utility Model Publication No. 63-101951, a bristle brush was installed near the blade to scrape off the accumulated toner, or air was blown in the direction of supply toward the m-retention toner. Method of providing a nozzle, (IF) JP-A-58-376
As shown in Japanese Patent Application No. 75, a method in which the blade is separated from the developing roller every time a certain number of copies are made, and the staying toner is conveyed to another area while remaining on the developing roller, (II
I) As shown in Japanese Patent Application Laid-Open No. 63-118170, a method has been proposed in which the developing roller is reversely rotated for a certain period of time or by a certain angle after the end of the developing process or before the start of the developing process to remove the accumulated toner. There is.

However, among the methods (I) above, the bristle brush method requires a large space between the developing roller and the blade to accommodate the bristle brush, so the angle between the developing roller and the blade is sufficient. It is applicable when the angle is large, but not applicable when the angle is small. Further, in the case of the air blowing type, since the air is sprayed in substantially the same direction as the toner supply direction, there is a risk that the toner may be ejected from between the developing roller and the blade and scattered to the outside. Furthermore, in both types, the bristle brush and nozzle themselves may disrupt the flow of toner.

On the other hand, when using the blade separation method (I), after the staying toner is conveyed to another area while being placed on the developing roller, a means for scraping off the staying toner and a container for collecting the scraped toner are provided. etc. are required separately, making the internal structure of the developing device complicated.

Furthermore, in this (n) method and the developing roller reverse rotation method tt*## of (I[[), the residual toner must be removed after or before the development process, which causes a large time loss .

Note that in order to ensure sufficient contact pressure even if toner accumulation occurs, it is possible to set the contact pressure high in advance, but this will increase the wear and tear on the blade and developing roller and also reduce the toner charge. This is not a good idea because the amount becomes too large and fogging etc. are likely to occur in the image.

On the other hand, as a method that can solve these problems all at once,
A method has been proposed in which air is blown toward the staying toner from both sides in a direction substantially perpendicular to the toner supply direction (see Japanese Patent Application No. 1-181436 filed by the present applicant).

According to this method, it can be applied to those with a small blade angle, and the structure is simple because only a means for air blowing is required. Further, the staying toner can be removed regardless of whether or not the developing process is in progress. Furthermore, since the air is blown from both sides in a direction almost perpendicular to the toner supply direction, there is no risk of disturbing the flow of the toner, and the blown toner may be ejected from between the blade and the developing roller. There is no risk of it scattering outside.

However, in this method, since the amount of air sprayed from both sides is always constant, if the amount of air sprayed l is small, the air will not reach the axially central portion of the developing roller sufficiently. Further, even when a large amount of air is blown, the collision point of the air from both sides is fixed at the center, so that the forces of the air from both sides cancel each other out at this collision point. thus,
Regardless of the amount of air being blown, a blind spot of air is formed in the central part, so that the problem remains that toner in this part remains and accumulates without being blown away.

Therefore, the present invention eliminates the drawbacks of the conventional method and uses a method of blowing air from both sides, while preventing the occurrence of an air blind spot in the center, which is a problem with this method, and reliably removing the accumulated toner. [Means for Solving the Problems] The present invention provides a developing device in which a developer is attached to the surface of a developer carrier and transferred toward a photoconductor, and a thin layer is transferred to the surface of a developer carrier. In a developing device configured to regulate the thickness of the developer by a forming member, form a thin layer of developer on a developer carrier, and then supply it to the photoreceptor, the developer supply direction on the developer carrier is provided. yAe by the thin layer forming member from both sides in a direction substantially perpendicular to
An air blowing means is provided for blowing air toward the area where the thickness of the developer is to be regulated, and the air blowing means includes an air supply device and air from the air supply device to positions on both sides of the developer carrier. The air supply device is provided with air supply passages on both sides that lead to air supply passages, and an air supply control device that changes the amount of air supplied to the air supply passages on both sides in a direction that is unbalanced on both sides.

Further, the invention of claim 2 provides the air supply control device according to the invention of claim 1 with two air supply ports that separately send air from the air supply device to both side air supply passages, and a It is constructed by a shutter that changes the opening amount of at least one air supply port so that the amount of air sent into the air supply path changes in a direction that becomes unbalanced, and a shutter drive device that drives this shutter.

[Effect]

With this configuration, the amount of air blowing from both sides changes so that it is unbalanced on both sides, so there is no dead spot in the air blowing in the center, and the accumulated developer can be reliably blown away without leaking. .

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

A basic embodiment of the invention is shown in FIGS. 1-5.

In this basic embodiment, 1 is a hopper containing toner D, 2 is a developing container, and these constitute a housing 3 of the developing device.

Inside the developing container 2, a developing roller 4 serving as a developer carrier is provided.
and a supply roller 5 are rotatably provided in contact with each other, and both O-rollers 4 and 5 are driven to rotate in the counterclockwise direction in FIG. 1 by a drive mechanism (not shown). .

The developing roller 4 is arranged near the photosensitive drum A, and a blade 6 as a thin layer forming member is arranged on the circumferential surface of the developing roller 4. This blade 6 is attached to the other end of a metal plate 8 having spring properties, one end of which is fixed to an inner plate 7 in the developer container 2, and when this gold WA root 8 is pushed down by a push cam 9, the blade The tip of the developing roller 6 is pressed against the circumferential surface of the developing roller 4 .

The push cam 9 is rotationally driven by a stepping motor 10, and the rotation of the push cam 9 changes the force for pushing down the metal plate 8, so that the contact pressure of the blade 6 against the developing roller 4 is adjusted. .

On the other hand, in both side walls 3a of the housing 3, a space surrounded by the lower surface of the blade 6 and the circumferential surface of the developing roller 4;
That is, at a position facing a part where the thickness of the toner layer is regulated by the blade 6 and where toner accumulation may occur (hereinafter referred to as the toner retention part),
Air outlets 11 and 12 (hereinafter referred to as first and second air outlets) are provided to open in a direction substantially perpendicular to the toner supply direction of the developing roller 4, and air is blown through these air outlets 11 on both sides by a means. Air is blown from .12 toward the toner retention area.

To explain the means for this air blowing, as shown in FIG. A device 16 is configured.

The fan box 14 of this air supply device 16 is provided with two air supply ports 17.18 (hereinafter referred to as the first and second air supply ports), and the air supply ports 16 and 17 are connected to each other separately. Air hose as air supply path 19.20
The tip of is the first. It is connected to both second air outlets 11 and 12. In this way, the air from the air supply device 16 is
Both air outlets 11 pass through this air hose 19 and 20.
12, from where it is sprayed toward the toner retention area.

However, if this is done alone, as described above, an air blind spot will occur at the center of the developing roller axial direction in the toner retention area.

Therefore, as shown in FIGS. 3 and 4.5, a semicircular shutter 21 is rotatably provided inside the fan box 14 at a position facing both air supply ports 17 and 18.

This shutter 21 rotates in synchronization with the fan 13 by a shutter rotation shaft 13b that rotates coaxially and integrally with the rotation shaft 13a of the fan 13, and the rotation of this shutter 21 causes the opening of both air supply ports 17 and 18. The amount is continuously and automatically adjusted in the direction of imbalance.

That is, FIG. 4 shows a state in which the second air supply port 18 is fully open and the first air supply port 17 is fully open. In this state, the entire amount of air from the air supply 6116 is fed into the first air supply port 17, and the air is blown only from the first air outlet 11 toward the toner retention area.

When the shutter 21 rotates in the direction of the arrow in Fig. 4.5 from this state, the second air supply port 1 opens as shown in Fig. 5 (a).
8 is open and the first air supply port 17 is closed,
The amount of air blown tends to decrease at the first air outlet 11 and increase at the second air outlet 12. Then, as shown in FIG. 5(b), the opening relationship of both air supply ports 17 and 18 is reversed, air blowing from the first air outlet 11 is stopped, and the second air outlet is Air is blown only from the opening 12 toward the toner retention area.

In this way, the air blowing from both outlets 11 and 12 is -
By continuously increasing and decreasing the amount of air in a direction that always creates an imbalance, air can be blown to the toner-accumulating area from one side only, from the other side, or from both sides with different strengths. The situation is constantly changing.

Therefore, there is no air blind spot in the toner retention area, and air can be evenly blown over the entire toner retention area, so that the toner in the central area is not removed forever as in the past, and 'IaTiB' is accumulated. It is possible to prevent the occurrence of such a situation and to reliably remove the staying toner without any leakage.

This air blowing means may be configured to operate automatically at fixed time intervals or every fixed number of copies, or may be operated at appropriate times by operating a switch from the outside depending on the image situation. However, in this embodiment, it is configured to operate automatically depending on the toner retention situation.

That is, as shown in FIGS. 1 to 3, the housing 3
facing the toner retention area and upstream of the air outlet 11.12 in the toner supply direction ili! A pressure sensor 22 as a toner retention detection means is provided at a position l.

This pressure sensor 22 detects the contact pressure with the staying toner D, and this detection signal is sent to a control device 23 comprising a microcomputer or the like as shown in the third factor. This control device 2
3, when the amount of toner staying exceeds a certain level, the pressure sensor 22
Only when the pressure detected by the air supply device exceeds the preset pressure! [It is configured to output an operating signal to the motor 15 that drives the fan 13 and shutter 21 of [16].

In this way, the actual amount of toner accumulated in the toner retention area is detected, and only when this amount of toner reaches a certain level or more,
As mentioned above, since the structure is configured to blow air to remove the accumulated toner, for example, if air is sprayed at fixed intervals regardless of the amount of accumulated toner or every fixed number of copies, As shown in the figure, the air blowing action may be wasted even though there is actually not much toner accumulated, or conversely, the timing of air blowing may be delayed and a large amount of toner may accumulate. Therefore, the accumulated toner can be effectively removed at an appropriate timing.

Note that other types of sensors such as a photo sensor may be used instead of the pressure sensor as the toner retention detection means.

On the other hand, if the edge device is sealed, the air blowing may sometimes increase the pressure inside the developing device, and there is a risk that the staying toner D may be ejected from between the blade 6 and the developing roller 4. Therefore,
As shown in FIG. 1, an air vent 24 is provided in the inner plate 7 of the developer container 2 in a vertically penetrating manner, and an air outlet 25 is provided in the top wall of the housing above the air vent 24. , the air blowing is sometimes configured such that the internal air of ω corresponding to the air acid escapes to the outside through the air vent 24 and the air outlet 25. Mesh plate 24 for preventing blown toner from scattering to the outside
A is provided.

Note that if there is no inner plate 7, there is no need to provide the air vent 24.

Other Embodiments Regarding the air supply control means, in the basic embodiment described above, by using a semicircular shutter 21, both air supply ports 1
However, as shown in FIG. 6, by using a shutter 26 with a short circumference, both air supply ports 17 and 18 can be simultaneously opened. Alternatively, one side may always be fully open to avoid this. Further, in the embodiment shown in FIG. 6, the radius of the shutter 26 is also made small, and both air supply ports i7.
18 is configured so that a portion thereof can be opened even in the maximum occlusion state.

Alternatively, as shown in FIG. 7, a notch 27a may be provided in the disc-shaped shutter 27, and the air supply port 17.18 may be opened by this notch 27a. Note that the notch 27a is connected to both air supply ports 17.1 as shown by solid lines in the figure.
It may be small enough to selectively open only one of the air supply ports 1 to 8, or it may be small enough to selectively open only one of the air supply ports
7 and 18 may be opened at the same time.

Furthermore, in each of the above embodiments, the opening amount of both air supply ports 17 and 18 is adjusted, but as shown in FIG. Then, the opening amount of only the second air supply 018) may be adjusted.

Additionally, a motor 1 for the fan 13 is used as a shutter drive device.
Alternatively, as shown in FIG. 9, a shutter 29 having blades 29a on the back side may be used, and the shutter 29 may be rotated by applying the air flow from the fan 13 to the blades 29a. You may also do so.

On the other hand, if it is desired to increase the force of air blowing, a compressor may be used as the air supply device.

Furthermore, the present invention is applicable not only to a developing device in which the contact pressure of the thin layer forming member with respect to the developer carrier can be adjusted, but also to a device in which the thin layer forming member is fixed in a fixed position. Can be done.

〔Effect of the invention〕

As described above, according to the present invention, the drawbacks of the conventional method are eliminated, and the air is blown from both sides, while the amount of air blown from both sides changes in a direction that creates an unbalanced state on both sides. Therefore, air blowing from both sides can prevent the generation of an air blind spot in the center, which is a problem with this method, and thereby the stagnant developer can be reliably removed without leaking.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing the first embodiment of the present invention, Fig. 2 is an enlarged view of the same part, Fig. 3 is an enlarged sectional view taken along the line ■-■ in Fig. 1, and Fig. 4 is Fig. 3 IV- IV line enlarged sectional view, Figure 5 (a) (
B) is a diagram corresponding to FIG. 4 for explaining the air supply control action by the shutter in FIG. 4, and FIGS. FIG. 9 is a schematic sectional view showing yet another embodiment. 4...Developing roller as a developer carrier, D...Developer (toner), A...Photosensitive drum, 6...WI
Blade as a layer forming member, 11.12...Air outlet, 19.20...Air hose as an air supply path, 16...Air supply device, 13...Fan configuring the device, 14...same fan box, 15...
Fan drive motor, 17.18... Air supply 1.
II IE air supply port, 21.26,2
7.28.29...The same shutter, a blade as a means.

Claims (1)

[Claims] 1. The developer is attached to the surface of the developer carrier and transferred toward the photoreceptor, and the thickness of the developer is controlled by a thin layer forming member so that the developer is transferred onto the developer carrier. In a developing device configured to form a thin layer of developer and then supply it to the photoreceptor, the thickness of the developer by the thin layer forming member is measured from both sides of the developer carrier in a direction substantially perpendicular to the developer supply direction. The air blowing means includes an air blowing means for blowing air toward a portion to be regulated, and the air blowing means includes an air supply device and both sides that guide the air from the air supply device to positions on both sides of the developer carrier. 1. A developing device comprising: an air supply path; and an air supply control device that changes the amount of air supplied to the both side air supply paths in a direction that creates an imbalance on both sides. 2. Two air supply ports that send air from the air supply device to both side air supply paths separately, and the amount of air sent from both air supply ports to both side air supply paths changes in a direction that becomes unbalanced. 2. The developing device according to claim 1, wherein the air supply control device is constituted by a shutter that changes the opening amount of at least one of the air supply ports, and a shutter drive device that drives the shutter.